It is well-known that various industrial and other products are damaged by the growth of microorganisms such as bacteria and fungi. Other examples of noxious animals and plants include wood-ingesting insects, aquatic animals and plants fouling ships and other marine constructions such as acorn shells and algae.
A number of agents are known and used in practice to control such noxious animals and plants. These agents are usually applied to an object to be protected as a solution or dispersion in a liquid binder, or as microcapsules incorporating an active substance in order to obtain a prolonged efficacy, although the active substance per se may be applied directly in certain cases.
Such liquid preparations have certain disadvantages in that the releasing rate of active substance is not constant and the length of the effective period is relatively short. Active substances are often not uniformily dispersed in the binder liquid or they may be susceptible to phase separation upon storage.
Microcapsules also have certain disadvantages in that they are incompatible with a liquid carrier such as organic solvents or water which swells or otherwise ruptures the capsule walls. It is generally difficult for microcapsules to control the releasing rate of an active substance in an optimum fashion. They are too large in size to form a thin film on a substrate.
It is also known that certain disinfectants such as quarternary ammonium salts or iodine based antiseptics may be adsorbed on ion exchange resins for use as a long lasting preparation. The application of this technique is limited to only ionizable active substances and the resulting preparations are not suitable for forming a film on a substrate due to their large particle sizes.